The outbreak of Ebola in West Africa will take about six months to bring under control, the medical charity Medecins Sans Frontieres (MSF) has disclosed.
Speaking in Geneva, MSF President Joanne Lui said there should be greater leadership from the World Health Organization (WHO).
Earlier, WHO said the scale of the outbreak appeared to be “vastly underestimated”.
It said in a statement that “extraordinary measures” were needed.
The epidemic began in Guinea in February and has since spread to Liberia, Sierra Leone and Nigeria.
So far, 1,069 people have died.
Ms Lui said that controlling the outbreak in Liberia – which has recorded more than 300 deaths – was vital to containing the epidemic.
“If we don’t stabilise Liberia, we will never stabilise the region,” she said.
“In terms of timeline, we’re not talking in terms of weeks, we’re talking in terms of months. We need a commitment for months, at least I would say six months, and I’m being, I would say, very optimistic.”
Ebola is transmitted by direct contact with the body fluids of a person who is infected.
Initial flu-like symptoms can lead to external haemorrhaging from areas such as eyes and gums, and internal bleeding which can lead to organ failure.